The objective of this study is to develop and utilize an animal model system to: (1) identify and classify all pregnancy-associated proteins detected by immunologic methods in pregnant, estrogen-treated, tumor-bearing and injured adult rats as either pregnancy-associated macroglobulin, pregnancy-specific protein, both analogous to their human counterparts, or as "acute phase" serum proteins known to be common to both pregnancy and non-specific trauma, (2) isolate and purify these different pregnancy-associated proteins by a combination of ultrafiltration, ammonium sulfate fractionation, iron-exchange and molecular exclusion chromatography, (3) investigate the origin and sites of synthesis of these pregnancy-associated proteins in pregnant, estrogen-treated and breast tumor bearing rats by 14 C-incorporation into immunochemically isolated proteins in vitro, and confirmation of synthesis by radioimmunoelectrophoresis and (4) compare the immunosuppressive effects of these purified rat pregnancy-associated proteins on lymphocyte blastogenesis induced by mitogens in vitro.